This invention relates to steam injected gas turbine engines, and, more particularly, to apparatus and methods for augmenting steam injection with water injection to thereby increase the power output of the steam injected gas turbine engine.
Steam injected gas turbine engines are known which use gas flowing therethrough following a Brayton Cycle and also having steam flowing therethrough which follows a Rankine Cycle. Frequently, aircraft derivative engines are used for such steam injected engines. The aircraft engine is modified to include an output power turbine, as well as additional fixed recuperative boilers at its output. The recuperative exhaust boilers provide the steam for injection into various locations of the engine, and especially to the combustor. While the steam could also be supplied from an external source, generally, the steam injected gas turbine engine is supplied with steam from its own exhaust boiler system.
One limitation on power output of the steam injected engine is that the steam from its own fixed boilers may not be of adequate low superheat to allow the gas turbine to run to its maximum capability. For example, the combustors could probably take more water vapor both in its dome and in its bypass diluent air which flows from the compressor discharge. However, because of the presence of the steam injection lines flowing into the combustor, there is no possibility provided for further water augmentation to the combustor to increase the amount of water vapor.